Despite the recognized environmental and health benefits of cycling, bicyclists are vulnerable to severe injuries and mortalities in the road crashes. Therefore, it is of paramount importance to identify the possible factors that may affect the bicycle crash risk. However, reliable estimates of bicycle exposure are often not available for the safety risk evaluation of different entities. The objective of this study is to advance the estimation of exposure in the bicycle safety analysis, using the detailed origin-destination data of each trip of the London public bicycle rental system. Two approaches including shortest path method (SPM) and weighted shortest path method (WSPM) are proposed to model the bicycle path choice and to estimate the bicycle distance traveled (BDT). Then, the bicycle crash frequency models that adopt BDTs as the exposure estimated using SPM and three WSPMs are developed. Three exposure measures including bicycle trips, bicycle time traveled (BTT), and BDT are assessed. Results indicate that the bicycle crash frequency models that incorporate the BDTs using WSPM have superior model fit. Moreover, the bicycle crash frequency model that incorporate the BDTs as the exposure outperforms those that incorporate the bicycle trips and BTT as the exposures. Findings of current study are indicative to the development of bicycle crash frequency model. Moreover, it should enhance the understanding on the roles of environmental, traffic and bicyclist factors in bicycle crash risk, based on appropriate estimates of bicycle exposures. Therefore, it should be useful to the transport planners and engineers for the development of bicycle infrastructures that can improve the overall bicycle safety in the long run.

尽管骑自行车对环境和健康有公认的好处，但骑自行车的人在道路交通事故中仍然容易受到严重伤害和死亡。因此，最重要的是确定可能影响自行车撞车风险的因素。但是，自行车暴露的可靠估算通常无法用于不同实体的安全风险评估。这项研究的目的是使用伦敦公共自行车租赁系统每次旅行的详细原点-目的地数据，提高自行车安全性分析中的暴露估算。提出了两种方法，包括最短路径方法（SPM）和加权最短路径方法（WSPM），以对自行车路径选择进行建模并估算自行车行驶距离（BDT）。然后，开发了采用BDT作为SPM和三个WSPM估算暴露量的自行车碰撞频率模型。评估了三种暴露度量，包括自行车旅行，自行车旅行时间（BTT）和BDT。结果表明，结合了使用WSPM的BDT的自行车碰撞频率模型具有出色的模型拟合度。此外，将BDT作为暴露的自行车碰撞频率模型要优于将自行车出行和将BTT作为暴露的自行车碰撞频率模型。当前研究的结果表明自行车碰撞频率模型的发展。此外，应根据对自行车暴露的适当估计，加深对环境，交通和骑自行车者因素在自行车撞车风险中的作用的了解。因此，